From the manpage: If c is not an unsigned char value, or EOF, the
behavior of these functions is undefined.
(So putting char into them directly is wrong)

This simplifies the code and should make it slightly faster

This fixes backend/builtin_parityl.c and backend/builtin_parityll.c.

If the peephole replaced the current node by another node
the corresponding value is live before the current node.

This fixes x86code/flags.c.

(see testsuite/backend/sparc_notconsts.c for an example)

The transformation (a << c1) | c2 => (a | (c2 >> c1)) << c1
is only valid if the lower bits of c2 are clean.

This fixes opt/pr37102.c.